Data services of the Global System for Mobile communications (GSM) have launched a new era of mobile communications. The early analog cellular modems had become unattractive to the market as they were slow and unreliable. Now the market for data is moving onwards (more bursty) and upwards (more traffic), and the standardization institutes are working towards higher data rates but more significantly also towards packet data services. This will certainly broaden the appeal to end users because data is routed more efficiently through the network and hence at lower costs, and also access times are reduced.
The general trend is for data applications to generate increasingly bursty data streams, this makes for inefficient use of a circuit switched connection. Moreover, fixed networks have seen an enormous growth in data traffic, not at least because of the rise of Internet access demand, such that it is to be supposed that mobile networks will spread as technology and customer expectations move on. The current GSM switch network is based on narrow band ISDN (Integrated Services Digital Network) circuits, so that the reason for rate limitations moves from the access network to the core network.
The new General Packet Radio Services (GPRS) network will offer operators the ability to charge by the packet, and support data transfer across a high speed network at up to eight times slot radio interface capacity. GPRS introduces two new nodes into the GMS network, a Serving GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN). The SGSN keeps track of the location of the mobile terminal within its service area and sends and receives packets to/from the mobile terminal, passing them on or receiving them from the GGSN. The GGSN then converts the GSM packets into other packet protocols (e.g. IP or X.25) and sends them out into other networks.
Services like multislot data and GPRS are very useful in moving the base technologies forwards, but if the same goals can be achieved with the existing data services, services on the current networks should be prototyped. Therefore, a standardized mobile access mechanism for fixed network services, focussing on increasing the effective throughput and immunity to dropped calls and thus reducing the needed airtime should be established. UMTS will deliver advanced information directly to people and provide them with access to new and innovative services. It will offer mobile personalized communications to the mass market regardless of location, network or terminal used.
Cellular radio frequencies are usually owned as licensed bands by the network operators. The huge licensing fees lead to rigid licensing procedures which make it difficult to maintain a healthy and non-discriminatory competition environment. Currently, a strictly separate usage of owned access resources by individual network operators can be observed. Hence, ownership of frequency bands or spectrum is considered to be a key factor of success for the operator's business.
To achieve a wide area coverage at increasing amounts of network traffic, smaller cell sizes are required, which makes network planning more and more difficult and leads to increased site acquisition costs and radio access network investments. Moreover, huge and rigid standardization efforts are required to introduce new access systems.
However, given the massive investments that have been made in existing networks of all types, and the enormous capital value that still attaches to most of them, operators and users will wish to continue to exploit them until the end of their useful lives. Almost all existing networks can be used as access networks for IP-based services. Therefore, interoperability between UMTS terminals and other IMT-2000 (International Mobile Telecommunications-2000) network family members, or even non-UMTS access networks is a key requirement. In particular, UMTS operators should be able to use common access networks owned by other access network providers, while the user has subscription only with the UMTS operator.